Vibratory system and apparatus



G. W. PIERCE VIBRATORY SYSTEM AND APPARATUS June 12-, 1934.

Filed April 23, 1928 Patented June 12, 1934 UNITED STATES PATENT OFFICE Application April 23, 1928, Serial No. 272,034 In Canada December 31, 1927 9 Claims.

The present invention relates to vibratory systems and apparatus, and more particularly to electrical systems and apparatus employing piezo-electric crystals.

The invention will be explained in connection which the accompanying drawing, the single figureof which is a diagrammatic view of apparatus and circuits constructed and arranged in accordance with the present invention for tele- 10 phone reception.

A piezo-electric crystal body 72 is shown pro-, vided with static potential plates or electrodes 74 that are connected inductively with input leads 12, 14 of a carrier-telephone system or car- 15 rier-telegraph system. The crystal 72 is preferably tuned to the carrier frequency so as to enable operation at the carrier telephone frequency,say 20,000 cycles per second, and it is preferably of low'decrement. Greater sensitiveness" and selectivity may, however, be obtained by electrically tuning the signal circuits, as by a condenser 13. If desired, the tuning condenser 13 may be inserted on the line side of the transformer 2'7 instead of, as shown. on the crystal sde' thereof. A carrier-telephone system is illustrated, the speech signals of which are transmitted as modulations of carrier current from a distant telephone transmitting station. The carrier current may be impressed upon the circuit 12, .14 by means of a transformer 27. The

electric currents arriving as incoming signals cause the crystal '72 to become deformed mechanically, or vibrate. These deformations vary the electrical conductivity of one or more microphones 15 that are attached to the crystal. The

current of a battery 11, sent through the microphone or microphones, becomes thus modulated in accordancewith the signal currents through the vibrations of the crystal body. The signals 40 of the transmitting station may, therefore, be

',detected in a telephone receiver 19. The receiver 19 may be in series with the local battery circuit, as illustrated, or it may be connected in the secondary circuit of a transformer the primary winding of which is in the local battery circuit. The carrier frequencyv is modulated by the speech vibrations, and the latter are accordingly transferred through the crystal body to the telephone receiver 19.

The modulations of local current may be caused to operatev a relay, insteadof the telephone receiver 19, or may be utilized in other desired ways, Thus, the 'relay may be caused to produce interrupted signals, for carrier-telegraph systems, the relay coil replacing the beforementioned primary transformer winding. The microphone or microphones 15 may be replaced by any other variable-resistance or variable-contact device, or by any equivalent device for varying the electrcal conductivity in responseto mechanical deformations of the crystal, and preferably attached to the crystal, or to some body that is vibrated by the crystal, such as a carbon plate or plates or an inertia-switch armature or armatures. It is not essential that the conduction-Varying device or devices be situated at the end or ends of the crystal. It or they may be placed free in space and be affected by air waves or other elastic waves.

The invention is also applicable to other uses, such as the production, as well as the reception. of carrier-telephone signals, and also to carriertelegraph signals, to the reception of radio signals, to beat-frequency signals of a radio system, to the control of frequency, speed 'or voltage of motor-generator sets, to the production of sustained oscillations at substantially constant frequency, whether with or without the use of a vacuum tube, and to amplifiers. It will, therefore, be understood that the invention is not limited to the exact form illustrated herein, but that it may be further modified and changed by persons skilled in the art without departing from its spirit and scope, as defined in the appended claims.

What is claimed is:

1. An electric system having, in combination, an alternating-current circuit for the flow of high-frequency currents, a piezo-electric crystal body responsive to the current flowing in the circuit and having a natural frequency of mechanical vibration substantially synchronous with a frequency of the alternating current of the circuit, a microphone the electrical conductivity of which is varied in accordance with the deformations of the body, and an electric circuit through the microphone and the electrical conduction of which is varied in accordance with the vibrations of the body.

2. A receiving system having, in combination, an alternating-current circuit for the flow of received carrier currents, a piezo-electric crystal body responsive to the current flowing in the circuit and having a natural frequency of mechanical vibration substantially synchronous with the carrier frequency, a current-varying element positioned to be mechanically actuated by the vibrations of the body, an electric circuit through the current-varying element and the electrical conduction of which is varied in accordance with the deformations of the body, and a translating device responsive to the variations in the electrical conditions of the second-named circuit.

3. A receiving system having, in combination, an alternating-current circuit for the flow of received carrier currents, a vibrator comprising a pieao-electric crystal capable of elastic vibrations responsive to the current flowing in the circuit vibrations from the crystal to the translating device.

4. An electric system having, in combination, an alternating-current circuit, means for supplying radio-frequency energy to the circuit, a piezoelectric crystal body responsive to the current flowing in the circuit and having a natural frequency of mechanical vibration substantially synchronous with a frequency of the alternating current of the circuit, a carbon-granule microphone mechanically associated with said crystal body, an electric circuit associated with said element and responsive by current variations to changes in said element, and means for indicating variation of current in said second-named circuit.

5. An electric system having, in combination, an alternating-current circuit for carrier frequency, a piezo-electric crystal body connected with the circuit and having a natural frequency of mechanical vibration substantially synchronous with the carrier frequency, a resistance mechanically connected with the crystal so as to be modified by the vibrations of the crystal, and an electric device controlled by the resistance.

8. An electric system having, in combination, an alternating-current circuit for carrier frequency, a circuit tuned to the carrier frequency, a piezo-electric crystal body connected with the second-named circuit and having a natural frequency of mechanical vibration substantially synchronous with the carrier frequency, a resistance mechanically connected with the crystal so as to be modified-by the vibrations of the crystal, and an electric device controlled by the resistance, the said device being responsive to a modulation frequency.

7. An electric system having, in combination, an alternating-current circuit for carrier frequency, a circuit tuned to the carrier frequency, a piezo-electric crystal body connected with the second-named circuit and having a natural frequency of mechanical vibration substantially synchronous with the carrier frequency, a resistance mechanically connected ,with the crystal so as to be modified by the vibrations of the crystal, and. an electric device controlled by the resistance, the'said device being-a telephone receiver responsive to a modulation frequency.

8. A receiving system having, in combination, a circuit for the flow ofreceived, radio-frequency, carrier currents, a piezo-electric crystal body tuned substantially to resonance with the said radio frequency, whereby the crystal body vibrates freely at a natural frequency of mechanical vibration corresponding to the said radio frequency, a microphone for demoduiating the received currents and associated with the crystal body so as to be vibrated mechanically thereby at the said radio frequency, means connecting the microphone in an electric circuit, whereby the electrical conductivity of the second-named circuit varies in accordance with the modulation frequency, and a device for indicating the demodulated current connected in the second-named circuit.

9. An electric circuit having, in combination, an alternating-current circuit, a piezo-electric crystal body responsive to the current flowing in the circuit and having a natural frequency of mechanical vibration substantially synchronous with a frequency of the alternating current of the circuit, whereby the crystal body vibrates freely at the said natural frequency, a microphone associated with the crystal bod so as to be vibrated mechanically thereby at e said natural frequency, means connecting the microphone in an electric circuit, whereby the electrical conductivity of the second-named circuit varies in accordance with the modulation frequency, and a current-indicating device connected in the second-named circuit.

GEORGE W. PIERCE. 

